The regulating member of a timepiece generally includes an inertia wheel, called a balance, and a resonator called a balance spring. These parts have a determining role as regards the working quality of the timepiece. Indeed, they regulate the movement, i.e. they control the frequency of the movement.
The balance and the balance spring are different in nature, which makes it extremely complex to manufacture the regulating member, the manufacturing including the manufacture of the balance and the balance spring and the resonant assembly of the two parts.
The balance and the balance spring have thus each been manufactured in different materials, particularly in order to limit the influence of a temperature change, but without resolving the difficulties as regards resonant assembly.